
body, html {  
    margin: 0;  
    padding: 0;  
    height: 100%;  
}  
  
body {  
 
    background-image: url('../课用图片/bk.png'); 
    background-attachment: fixed; 
    background-position: center; 
    background-repeat: no-repeat;  
    background-size: cover; 
}  
header{
    background-color: white;
    height:80px;
    width: 100%;
    position: relative;
    display: flex;  
    justify-content: space-between;   
    align-items: center;   
    padding: 0 20px; 

} 
header ul {  
    display: flex;  
    list-style: none;  
    margin: 0; 
    padding: 0; 
    height: 100%;  
}  

header li{
    display: inline;
    margin-right: 4vw;
}
    header ul{
        position: absolute;
        top:0;
        right: 5px;
        line-height: 50p;
}
header a{
    color:black;
    text-decoration: none;
}
header a:hover{
    text-decoration: underline;
}
.content {  
    padding: 20px;  
    font-family: Arial, sans-serif;  
    text-align: center;  
    background-color: rgba(255, 255, 255, 0.8); 
    padding-top: 100px; 
}
.line{
    padding: 0%;
    margin: 0%;
}


ul{
   list-style-type: none;
}
.tie {  
    width: 30%; 
    padding: 0px;
    margin: 0px;
 
}  
  .nancy{
margin-left: 500px;
margin-right: 100px;
padding: 20px;
    box-shadow: 10px 10px 5px rgba(0, 0, 0, 0.3);
    background-color: white;
    justify-content: right;
  }
.xi{
    height: 30px;
    padding-left:500px ;
    padding-bottom: 0px;
    margin-bottom: 0px;
    color: rgba(128, 128, 128, 0.5); 
    border-bottom: 2px solid red;
}
.paragraph{
    border-bottom: 2px solid lavender;
}
li {  
    display: inline-block; 
    margin-right: 20px; 
}  
.bottom{
    margin-left: 400px;
}
.red{
     position: absolute;
     left: 70px;
     top: 50%;
    height: 200px;
    width: 200px;
     border:10px solid rgba(173, 9, 9, 0.955);
     border-top-left-radius: 0;
     border-top-right-radius: 0;
     border-bottom-left-radius: 0;
     border-bottom-right-radius: 50px;
    background-color:  rgba(173, 9, 9, 0.955);
     }
     .red a{
    color: antiquewhite;
    }